Mystery more or less solved. The bolts on the LIM were still tight, so I pulled the LIM and the exhaust manifold off. The LIM-to-engine gasket was still in decent shape. However, both of the coolant o-rings had split in half. This still doesn't really tell me why there was oil pooling on there, but oh well...
Since I've gone this far, it looks like I will be blocking the rear iron and manifold coolant ports. I figure if I just put on a turbo that doesn't need coolant fed to it, there is no more chance of coolant leaks....
